1. Field of the Invention
This invention relates to an automatic exposure control device for a single lens reflex camera, and more particularly to an automatic exposure control device in which exposure factors are treated in the form of digital signals by use of pulses.
2. Description of the Prior Art
In the conventional automatic exposure control device for a single lens reflex camera, the scene brightness is measured before the shutter is released and the measured scene brightness is memorized in a memory in the camera so as to be used for controlling exposure when the shutter is released. The exposure control is conducted by controlling the exposure time or the aperture size of a diaphragm. It has been known in the art to memorize the measured scene brightness in the form of digital value. The digital type control system has been proved advantageous in various points than the analogue type control system in the field of exposure control. In the digital type exposure control system, the number of pulses of clock pulses generated from a pulse generator is counted. The digital type exposure control system has a defect in that it is very difficult to accurately start the counting of the clock pulses simultaneously with the start of a leading blind of a shutter. From the viewpoint of accurate exposure control, it is of course desired that the counting of the clock pulses be started simultaneously with the start of running of the leading blind of the shutter.